Which statement about identification is true for laboratory mice?

• A. Ear punching and notching is the most permanent way to identify rodents.
• B. Ear tagging is more permanent than ear punching.
• C. Visual fur color is always unique.
• D. Tail branding is standard practice.

Answer: (A)

In mice, identifying individuals relies on marks that last over the animal’s lifetime. Ear punching or ear notching creates a permanent scar in the ear cartilage, which is very durable and remains readable even as the animal grows and fur changes. This makes it the most reliable long-term identification method among common options.

Ear tagging, while useful for short-term identification, tends to be less permanent because tags can shift, become obscured by fur, or fall out, making reads during later checks unreliable.

Relying on visual fur color isn’t dependable because color patterns are not unique to individuals; many mice share similar colors, and coat changes can occur with age or in different lighting.

Tail branding is not standard practice in laboratory mice due to welfare concerns and the higher risk of injury or distress, so it isn’t commonly used.

So, the statement about ear punching and notching providing the most permanent identification best reflects how these methods are used in practice.